A sensitive, quantitative assay has been developed to study the biologic effects of the DNA viral intermediate and provirus of mammalian C-type RNA viruses. This procedure is being used to assess the ability of DNA to be infectious and/or to induce cellular transformation. Optimal conditions for extraction and titration of viral-specific DNA have been defined. The effect of chemical and physical treatment on virus expression will be evaluated. Differences between unexpressed and expressed will be evaluated. Differences between unexpressed and expressed endogenous and exogenous viral genomes are under study.